points out you are not allowed to modify the NationalProblemLibrary files so for those you need to make local copies. The setOrientation homework set is special since it is very often customized. Hence we provide each course with its own copy so that it can be customized in place.
You can also make a copy in another subdirectory but you need to make sure that the macro file parserOrientation.pl is still in the search path for the file.
The search path is (unless it's modified) (1) the same directory that the question file is in (2) the courses macro directory (3) any macro directories for the various libraries that have been included in the path, (4) the main webwork site collection of macro files. The search path is set in the global.conf directory which is set by the site manager.